1. Field of the Invention
This invention relates to material handling systems and more particularly to an automated depalletizer for use in a material handling system.
2. Description of Related Art
Material handling systems are commonly used to move materials in warehouses and the like, preferably with a minimum of human labor. In a typical warehousing operation, pallets loaded with articles, or units, such as cartons or other loaded containers are transported to a warehouse or distribution center. There, the goods are depalletized, i.e., removed from the pallets, and stored in the warehouse or directed elsewhere for further distribution. The depalletizing operation is performed primarily by human labor. It is, therefore, a relatively expensive and time consuming operation. It is also an operation which leads to injuries since the individual units to be handled may weigh on the order of 60 lbs. or more and a great deal of reaching is often required. Attempts have been made to automate the unloading of pallets. A complication, however, in automatic depalletizing is that the units loaded on the pallets are often not of uniform dimensions and a variety of sizes and shapes of units must be accommodated. Also, the units must be handled with sufficient care to avoid damage. Furthermore, the orientation of the units as they are unloaded from the pallets onto a conveyor or the like may have to be controlled. Particularly in cases where a certain side of the unit must be read by a bar code reader or the like.
One known depalletizer is disclosed in U.S. Pat. No. 4,106,635 entitled Elevatable Depalletizing System. That system includes a lift table, supported on a tiltable mast, used to raise the loaded pallet to the level of a chute. The tiltable mast is tilted until the articles of the uppermost layer begin to slide off. The chute includes a stopper mechanism which allows only one row of a layer of articles to slide off at a time. A problem with this prior art arrangement is that it relies on the angle of tilt of the mast to remove the individual units from the pallet. While that may be effective for certain goods, it will tend to cause units with a relatively small base, compared to its height, to topple. That may cause damage, but will also change the orientation of the unit in an unacceptable way. The chute mechanism allowing only one row to be removed at one time adds delay and reduces system throughput.